(NEWSER) – Amid Adolf Hitler's staggeringly horrific crimes against humanity, some pretty heavy-duty tax evasion appears to have been overlooked, a new British documentary set to air Friday finds.

The Hunt for Hitler's Missing Millions argues that the Fuhrer had plenty of money-making schemes, the Mirror reports: He copyrighted his own image, allowing him to rake in royalties from stamps sold bearing his image; was paid for public speeches; and made at least $1 million a year in royalties from Mein Kampf, thanks in part to the fact that a copy was given to all German couples on their wedding day. The documentary makers believe that Hitler owed at least $3 million in back taxes (in today's dollars) by 1938—though tax authorities were presumably a little reluctant to launch an investigation.

"Hitler's actual tax records survive and suggest that he was a 'cash-in-hand' businessman and a serial tax evader. He owed the German taxman a small fortune when he became supreme leader in 1933," one of the documentary makers tells the Daily Mail. The unpaid taxes added to a secret fortune that Hitler's Fortune author Chris Whetton, a contributor to the documentary, believes added up to more than a billion Reichsmarks, or more than $6 billion in today's money, at its apex. Hitler "felt paying taxes was beneath him," says Whetton, who believes Hitler's billions could still be stashed in secret accounts. (It's not the only claim of secret Nazi riches.)